The EU's cyber security agency, ENISA, has published a study on the botnet threat and how to address it.
The report makes recommendations for all groups involved in the fight against botnets.
An increasing proportion of cybercrime, such as spamming and automated theft of credit card details, is being channelled through botnets - networks of computers used without their owner's knowledge.
The report details how to assess botnet threats and how to neutralise them, and includes a survey and analysis of methods for measuring botnet size and how best to assess the threat posed by botnets to different stakeholders, a survey and analysis of botnet countermeasures, and 25 different types of best practices to attack botnets.
These include neutralising existing botnets, preventing new infections and minimising the profitability of cybercrime using botnets.
Alongside the main report, ENISA has set out the top 10 key issues for policymakers.
The document is based on ENISA's consultation with experts from all stakeholders, including Internet Service Providers (ISPs), security researchers, law enforcement, Computer Emergency Response Teams (CERTs) and anti-virus suppliers.
The document examines the role of governments in the fight against botnets, what is needed from legislation and where investment is required.
The recommendations cover legal, policy and technical aspects of the fight against botnets and give targeted recommendations for different groups involved, including the clarification of defensive measures permitted in each member state, measures for encouraging users to keep their computers free of botnets, and supporting schemes for ISPs to notify infected customers.
The report also emphasises the need for a close international co-operation between governments, technically-oriented, and legislative institutions.
"Global co-operation is indispensable for successful defence against botnets" says Udo Helmbrecht, executive director of ENISA.